During the first five yars of this grant a consortium of four Greater Boston institutions was establishd to study the anatomy and physiology of the vertebrate auditory system. This renewal application proposes to continue this work. Experiments on lizards and cats explore the physiological mechanisms at successive levels of the system: the middle ear, cochlea, auditory-nerve, cochlear nucleus, and more central locations. The work on animals can be related to human studies so that animal models of some auditory disorders are available. The results might have implications for both the dignoses and treatment of hearing defects having either peripheral or central origins.